Improving tribological and corrosion resistance of Ti6Al4V alloy by hybrid microarc oxidation/enameling treatments

A promising duplex coating was prepared by microarc oxidation (MAO) and enameling processes onto polished Ti6Al4V alloy. The TiO2 ceramic coating deposited by MAO was characterized and then combined with an enameling treatment in order to improve the tribological and corrosion resistance of Ti6Al4V alloy. The morphology, phase composition, and hardness of MAO and MAO/enameling-coated Ti6Al4V alloy were evaluated by scanning electron microscopy (SEM), X-ray diffraction (XRD), and Vickers microhardness tester, respectively. The tribological performance was investigated using a ball-on-disk tribometer. The corrosion resistance was studied using immersion tests and potentiodynamic polarization. Wear tests show that the enamel coating on the MAO-coated surface causes a reduction in the friction coefficient. Immersion tests demonstrate that the duplex coating is more effective in improving the corrosion resistance of Ti6Al4V than the MAO coating especially at high temperature (80 °C). Potentiodynamic polarization curves reveal that the corrosion potential of the duplex coating increases by about 250 mV and the corrosion current density is slightly lower than that of the MAO coating. The duplex coating is superior to the stand-alone MAO coating in improving the tribological and corrosion behavior of Ti6Al4V.